HU182548B - Process for producing methacrilic acid from methacrolein with catalytic oxidation - Google Patents

Abstract

The invention relates to a process for the preparation of a catalyst having a structure of a heteropoly acid and having the general formula: Mo & inda! V & indb! P & indc! Cu &dgr; As & inde! X & indf! O & indg !, where X is one or more elements selected from the group consisting of tin, lead, cerium, cobalt, iron, zirconium, thorium, tungsten, germanium, nickel, rhenium, bismuth, anitmonium, chromium, boron, magnesium, silver, aluminum, zinc and titanium. and a, b, c, d, e, f and g correspond to the atomic ratio of the elements, where a is equal to 10; b corresponds to a number equal to 3 or less than 3, excluding 0; c is a number equal to 0.5 to 6; d corresponds to a number equal to 3 or less than 3, excluding 0; e is a number equal to 3 or less than 3 excluding 0; f is a number equal to 0 to 3 and g corresponds to a number determined by the valency and atomic ratio of other elements by reaction of the starting materials of the elemental constituents in water or an organic solvent and evaporation to dryness.

Description

The present invention relates to a novel process for the production of methacrylic acid by catalytic oxidation of methacrolein. The oxidation is carried out using a new catalyst with high catalytic activity, very high selectivity and long life.

Although several processes have recently been proposed for the vapor phase catalytic oxidation of methacrolein, none of these have been commercially implemented, although the production of acrylic acid by acrolein oxidation is a well-known, industrial process. The difficulty is primarily due to the fact that the final product can be produced in substantially lower yields than the acrylic acid in the oxidation of methacrolein, and that most known catalysts have a life span too short to expect stable catalytic activity over a long period.

Most of the catalysts proposed for the vapor phase catalytic oxidation of methacrolein contain molybdenum phosphorus as the main component and are chemically considered as phosphomolybdate, such as the ammonium or alkali metal salt of the corresponding heteropoly acid.

The main disadvantage of these catalysts is their short catalytic lifetime, which is attributed to the fact that the structure of the heteropoly acid slowly decomposes under longer exposure and shows crystal growth of VIoO _{3 by} X-ray diffraction. These changes result in a decrease in catalyst activity. Thus, known catalysts are unsuitable for industrial applications because of their short catalytic lifetime, or catalytic oxidation must be carried out under mild conditions which make the preparation of the desired product extremely uneconomical.

Catalysts for the oxidation of methacrolein are described, for example, in U.S. Patent Nos. 3,875,220 and 4,001,316. However, using the catalysts shown, methacrylic acid can be obtained only in poor yields.

The process described in U.S. Patent No. 3,875,220 is also disadvantageous because the oxide mixture containing molybdenum, vanadium and phosphorus is prepared in the form of a slurry which requires further drying.

The preparation of a stable heteropolyacid catalyst is described in German Patent Publication No. 2,739,779. The structure of the catalyst can be illustrated by the formula Mo-P-V-Al-Y-0, where Y is a variable meaning, for example, a copper atom. Using the catalyst, methacrylic acid is still not completely recovered.

Based on our attempts to overcome the disadvantages of the known catalysts, it has been found that the use of a catalyst containing Mo-V-P-Cu-As elements which additionally contains one or more other elements, such as tin, lead, magnesium, has a great effect on the oxidation efficiency of methacrolein. .

1

According to the present invention, the present invention provides a process for the production of methacrylic acid by oxidation of methacrolein with molecular oxygen or gas containing molecular oxygen, in a vapor phase, in the presence of a mixed metal catalyst, in a vapor phase comprising:

Mo is _a catalyst of the formula Z 2, P _c Cu _rf As _e X _e 0 (where

X can represent one or more of tin, lead, cerium, cobalt, iron, zirconium, thorium, tungsten, germanium, nickel, rhenium, bismuth, antimony, chromium, boron, magnesium, silver, aluminum, zinc and titanium, b, c, d, e, f and g represent the atomic ratio of the elements and may have the following meaning:

a is 10 b is a number from 0.5 to 2, c is a number from 0.5 to 3, d is a number from 0.05 to 1, e is from 0.05 to 1 is a number from 0 to 3 and g is a number defined by the valence and atomic ratio of the other elements.

Especially preferred in the meaning of X are tin, thorium, cerium, tungsten, germanium, rhenium, bismuth, antimony, boron and aluminum.

X-ray diffraction studies confirm that the catalyst used in the present invention has a heteropolyolic acid structure and has characteristic diffraction peaks at 20 = 8.0 °, 8.9 ° and 9.3 °. Although the basic compound of the catalyst is a phospho-vanadium molybdic acid, its other constituents contribute to the improvement of catalytic activity and selectivity and increase the stability of the catalyst by replacing some of the elements of the phospho-vanadium molybdic acid and integrating it into the structure of the heteropoly acid.

The catalyst of the present invention is water-soluble by its heteropolyolic acid structure. However, it may contain water-insoluble components, such as oxides of the components, but these are said to have no effect on the catalyst's function.

In carrying out the process according to the invention, the catalyst is in reduced form since it is reduced with the feed containing methacrolein already in the initial stage of the reaction. Alternatively, the reduced form may be obtained by the use of reducible elements in the construction of the catalyst and addition of a reducing agent to the catalyst or treatment of the catalyst with a reducing gas.

The above catalyst is well suited for industrial applications because of its excellent activity, high selectivity and very long life. The catalyst can be used to produce methacrylic acid at high volumetric rates because increasing the volumetric rate has no significant effect on the results obtained. The catalyst - · as mentioned above - is water soluble, which has the additional advantage of being easy to apply on a support and easy to regenerate 3

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1 to dissolve catalyst material deactivated after prolonged use in water.

The catalyst may be prepared by a variety of methods known in the art for the preparation of heteropoly acids, but particular care must be taken to avoid the formation of an ammonium salt of the heteropoly acid.

For example, the catalyst used in the process of the invention may be prepared as follows:

The starting materials are reacted with one another in aqueous or organic solvents, and the product, when formed as an ammonium salt, is converted to the corresponding acid, extracted if necessary, and evaporated to dryness. The ammonium salt can be converted to the corresponding acid by conventional means, for example, ethereal extraction from an acidic aqueous solution, ion exchange or other known means. The product obtained can be extracted with any suitable organic solvent, such as ether.

In a particularly preferred process, the starting materials, such as the oxides or phosphates of the components, are dispersed or dissolved in water and then reacted with one another under heating, optionally with hydrogen peroxide, and finally, if desired, the insoluble components removed, evaporated to dryness or -anadium molybdic acid is reacted with oxides, phosphates, sulfates of building blocks and other similar chemical compounds.

In preparing the catalyst, the catalyst elements forming starting material may be different from the compounds, the only condition introduce only product heteropoly acid structure and not to the ammonium salt structure of the circumstances, the ^T hogj catalyst preparation.

Starting materials suitable for the introduction of the molybdenum component include, for example, molybdenum trioxide, molybdenum acid or salts, heteromolybdic acid cutting salts and molybdenum metal.

Starting materials suitable for introducing the phosphorus component include orthophosphoric acid, phosphoric acid, hypophosphoric acid or salts thereof, and phosphorus pentoxide.

Vanadium can best be incorporated into the catalyst using vanadium pentoxide, vanadium oxalate, vanadium sulfate, vanadium acid or its salts, or vanadium metal.

Starting materials for copper incorporation include copper oxide, copper phosphate, copper sulfate, copper nitrate, copper molybdate, and metal copper.

The arsenic component can be incorporated into the catalyst starting from, for example, arsenic trioxide, ortho-arsenic acid, metharenic acid, pyro-arsenic acid or salts thereof.

The starting material for the incorporation of component X can be oxides, phosphates, nitrates, sulfates, carbonates, molybdates and the corresponding metals.

Although the catalyst prepared according to the invention exhibits excellent catalytic activity per se, its thermal stability and lifetime, as well as the yield of the methacrylic acid produced by its use4 <

can be increased when applied to a suitable carrier. Preferred carriers are, for example, silicon carbide, aluminum powder, diatomaceous earth, titanium oxide, α-alumina. Active carriers reacting with the heteropolylic acid are not preferred.

The calcination step generally required for the preparation of the catalysts is not required during the catalyst preparation process of the present invention. Thus, it can be stated that the process according to the invention is easier and less expensive to produce a catalyst than conventional techniques.

Molecular oxygen or molecular oxygen containing gas is used for the oxidation of methacrolein according to the invention, preferably in an amount such that the molar ratio of oxygen to methacrolein is 0.5 to 10, more preferably 2 to 5.

Preferably, water vapor is also added to the feed gas in an amount of from 1 to 20, preferably from 2 to 15 molar, based on methacrolein.

The feed gas may additionally contain inert gases such as nitrogen, carbon dioxide, saturated hydrocarbons. The gas mixture obtained by the catalytic oxidation of methacrolein by isobutylene or tertiary butanol can be used directly for the purpose of the invention.

The reaction temperature is preferably 200-380 ° C, more preferably 250-350 ° C.

The amount of gas mixture fed, expressed in terms of space velocity, is generally 100-5000 hours ^-1 , preferably 500-3000 hours ^-1 , whereby the space velocity (SV) is expressed according to the NTP standard. Since the increase in spatial velocity (SV) has no particular effect on the reaction using the catalyst prepared according to the invention, the reaction can be carried out at high spatial velocity.

Although the reaction may be carried out at or above atmospheric pressure, it is preferred to carry out the reaction at near atmospheric pressure. The preferred pressure range is between 1 and 5 atoms.

Catalytic reaction of találmánj- can be conducted in any known reactor types such as fixed bed, fluidized bed ⁷ cut moving bed reactors as well.

In the following examples, the oxygen in the catalyst is not discussed because its amount is determined by the atomic ratio and valence of the other elements.

The conversion of methacrolein, the methacrylic acid yield, and the selectivity of the reaction are determined as follows:

conversion (%) of reacted methacrolein (mole) of methacrolein - X 100 Feeded methacrolein (mole) yield of methacrylic acid (mole) obtained (%) = -X100 feed methacrolein (mole) - selectivity of methacrylic acid yield (%) XlOO.

methacrolein conversion

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Example 1

100 g of molybdenum trioxide, 6.3 g of vanadium pentoxide, 1.1 g of copper oxide, 8.0 g of orthophosphoric acid and 1.8 g of pyro-arsenic acid are dispersed or dissolved in 1000 ml of deionized water. The resulting mixture was stirred and refluxed for 6 hours. The resulting clear orange-red solution was evaporated to dryness on a water bath. The resulting solid (catalyst) has the following composition: Mo ₁₀ V ₁ P ₁ Cu ₀ , ₂ As ₀ , ₂ . The product has a X-ray diffraction pattern and is a heteropolyolic acid with the following characteristic diffraction peaks: 20.0.0.0, 8.9 °, 9.3 °.

The product obtained was ground to a size of 24 to 48 mesh, then filled into a Pyrex glass reactor tube of 18 mm internal diameter and immersed in a fluidized bed. The oxidizing gas mixture containing methacrolein, oxygen, nitrogen and water vapor (1: 2.5: 14: 7) was passed through the tubular reactor at a space speed of SV = 1600 hours ^-1 and oxidation was continued at 320 ° C for 120 days. The results are shown in Table 1.

After 120 days, the structure of the catalyst was re-examined by X-ray diffraction and found that no molybdenum trioxide was formed and the structure of the catalyst did not change.

Example 2

Using 100 g of molybdenum trioxide, 6.3 g of vanadium pentoxide, 1.1 g of copper oxide, 8.0 g of orthophosphoric acid, 1.8 g of pyro-arsenic acid and 2.1 g of tin oxide as the starting material according to Example 1. The following process is used to prepare the catalyst having the following composition: Mo ^ V ^ Cu ₀ , ₂ As ₀ , ₂ Sn ₀ , ₂ . X-ray diffraction showed the solid to be a heteropolyolic acid with the following most characteristic refractive peaks: 20.0.0.0, 8.9 °, 9.3 °.

Under the conditions described in Example 1, methacrylic acid was continuously produced for 30 days using the resulting catalyst. The results obtained are also shown in Table 1.

3-21. examples

Instead of 2.1 g of tin oxide in Example 2, 3.2 g of lead tetroxide, 2.4 g of cerium oxide, 1.1 gtricobalt tetroxide, 1.1 g of iron oxide, 1.7 g of zirconium oxide .

3.7 g of thorium oxide, 3.2 g of tungsten trioxide, 1.5 g of germanium oxide, 1.0 g of nickel oxide, 3.4 g of rhenium hepttoxide, 3.2 g of bismuth oxide, 2.0 g of antimony. trioxide, 1.4 g of chromium trioxide, 0.9 g of boric acid, 0.6 g of magnesium oxide, 1.6 g of silver oxide, 0.7 g of alumina, 1.1 g of zinc oxide and 1.1 g Using titanium oxide, the products listed in Table 1 are obtained. The obtained products were found to be heteropolyolic in structure according to X-ray diffraction measurements and showed the following characteristic peaks: 20 = 8.0 °, 8.9 °, 9.3 °.

A series of experiments were performed under the conditions given in Example 1. The results obtained, is

Table 1 shows.

after a reaction time of one day, the structure of the catalyst was not changed by X-ray diffraction.

Table 1

Example number Composition of the catalyst Running Time (Sun) Reakcióhő- moderation (° C) methacrolein conversion (%) selectivity (%) methacrylic mining (%) First MOjoVjPjCUq, 2 A s ₀ , ₂ 1 320 93.4 83.6 78.1 120 320 93.5 83.9 78.4 Second ^ f ° 10 ^ 1 ¹⁵ l ¹ - ^zU 0'2-4 ^S 0! 2® ⁿ 0> 2 1 320 91.2 83.9 76.5 30 320 92.1 83.3 76.7 Third Μο _1θ Υ ₁ P ₁ Cu ₀ , ₂ As ₀ , ₂ Pb ₀ , ₂ 1 330 90.4 82.2 74.3 30 330 91.2 83.3 76.7 4th ^ ° 10 ^ ^/ l ^li l ¹ - ' ^u 0> 2-4 ^s o-2 ¹ -' ^e 0'2 1 315 92.5 81.5 75.4 30 315 92.2 81.8 75.4 5th ^ ° 10 ^ 1-Pl ¹ - ' ^U 0'2 ^ ^S 0> 2 ¹ ^ ^O 0'2 I 312 95.7 80.9 77.4 30 312 96.0 80.8 77.6 6th ^ - ^O 10 ^ 1 ^ ^> l ¹ - ' ^U 0'2 ^ ^S 0>2-®' ^e 0> 2 1 315 94.1 82.1 77.3 30 315 94.7 82.1 77.7 7th Mo ^ V ^ / ^ Ju ^ As Zr ^ 1 317 93.8 83.7 78.5 30 317 93.1 83.9 78.1

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Example number Composition of the catalyst Running Time (Sun) Reakcióhő- moderation (° C) methacrolein conversion (%) Selectivity Methacrylic acid (%) mining (%) 8th MojoVjPjCuo.ijASojjTho ^ 1 320 92.2 82.4 76.0 30 320 92.8 82.1 76.2 9th ^ ⁰ ioViPiUu ₀ , 2Aso, ₂ W ₀ , 2 1 325 90.4 83.7 75.7 30 325 90.1 84.0 75.7 10th Moi0ViPiCu _o , ₂ As _o , 2Ge _o , 2 1 320 92.0 82.8 76.2 30 320 92.7 82.6 76.6 11th 1 320 94.9 82.7 78.5 30 320 94.4 83.4 78.7 12th ^ θ10 ^ ΐΡΐ {- '' ^Ι 0> 2 ^ ⁸ 0'2Η ^β 0> 2 1 320 94.1 80.5 75.8 30 320 93.7 81.1 76.0 13th 1 320 96.0 81.3 78.0 30 320 95.5 81.7 78.0 14th 1 330 90.9 84.0 76.4 30 330 91.5 83.8 76.7 15th MojoV ₁ P ₁ Cu ₀ , ₂ As ₀ , 2Cr ₀ , ₂ 1 320 91.3 83.6 76.3 30 320 90.6 83.3 75.5 16th ^ ΘκΎιΒιθΊο, ϊΑβθ Β ^,) ^ 1 320 89.9 83.7 75.2 30 320 90.3 83.1 75.0 17th M ^ ^ UQ QViP AS ^ ^ ^ gMgQ 1 320 92.4 83.4 77.1 30 320 92.3 83.7 77.3 18th Moj ₀ V ₁ PiCu ₀ , ₂ As ₀ , ₂ Ag ₀ , 2 1 330 95.3 81.4 77.6 30 330 95.4 81.7 77.9 19th 1 330 92.7 83.0 76.9 30 330 91.9 83.0 76.3 20th Mo ViPjCujpjASo ^ ^ ^ ZnO 1 320 91.4 82.7 75.6 30 320 92.1 82.8 76.3 21st MOjoViPjCu ^ A ^ ^ Ti 1 330 93.3 80.9 75.5 30 330 92.9 81.6 75.8

22-25. example

Using the procedure of Example 1, 40 dried products listed in Table 2 were prepared and then examined by X-ray diffraction. We have found that they have a structure of heteropoly acid.

The resulting catalysts were used for the continuous production of methacrylic acid under the reaction conditions described in Example 1. The results obtained a

Table 2 shows.

X-ray diffraction showed no change in the composition of the catalyst during continuous operation for a day.

Table 2

Example number Composition of the catalyst uptime (Sun) Reaction- temperature (° C) methacrolein conversion (%) Selectivity Methacrylic acid (%) mining (%) 22nd Mo _M V ₁ PiCu ₀ , 2As ₀ , ₂ Sn ₀ , ₁ Pb ₀ , j 1 320 93.4 82.4 77.0 30 320 92.8 82.9 76.9 23rd Μο _ω V ₁ P ₁ Cii0, ₂ As _o ,. ₂ Ge _o , ₁ l \ i _{0> 1} 1 320 94.0 83.1 78.1 30 320 93.9 83.3 78.2 24th Mo ₁ 0V _l PjCu _o , ₂ As _O) 2Bi _o , _I Cr _o , j 1 320 94.8 81.1 76.7 30 320 94.8 81.6 77.4 25th ΜθκΑιΡι ^ ιιθ ^ ΑΒθ, ₂ AIq, | TÍ0, ₁ 1 320 92.9 80.8 75.1 30 320 93.6 81.0 75.8

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26-31. example

Using the procedure of Example 1, the catalysts listed in Table 3 were prepared and then examined by X-ray diffraction. We have found that they have a structure of heteropoly acid.

The resulting catalysts were used for the continuous production of methacrylic acid under the reaction conditions described in Example 1. The results are shown in Table 3.

X-ray diffraction measurements showed no change in the catalyst composition during 30 days of continuous operation.

Table 3

Example number Composition of the catalyst uptime (Sun) Reakcióhő- moderation (° C) methacrolein conversion (%) Selectivity Methacrylic acid (%) mining (° o) 26th ^ ° 10 ^ Ι'δ ^ Ι ^ Ο'δ Α®οί 1 34.5 91.3 80.1 73.1 30 345 92.0 80.3 73.9 27th Mo _ie Vj P ₃ Cu ₀ , ₅ As ₀ , jSn ₀ , i 1 340 87.1 75.5 65.8 30 340 87.0 75.6 65.8 28th Mo ₁₀ V ₀ , ₅ P ₁ Cu _e , ₀₅ As ₀ , ₀₅ Sn ₀ , ₂ 1 320 90.0 75.8 68.2 30 320 89.8 75.6 67.9 29th Mo ₁ 0Vi, ₅ P ₁ Cuj, _o As _o , ₂ N i ₀ , ₂ I 330 91.4 78.4 71.7 30 330 90.2 77.7 70.1 30th MojijVjP.jCuQjjAsojjGepo 1 335 92.7 80.5 74.6 30 335 92.3 81.0 74.8 31st 1 340 87.5 79.9 69.9 30 340 87.8 79.2 69.5 32-33. example space velocity (SV) was changed. The resulting origin '

Table 4 below. Using the catalyst of Example 6, the spit shows that the essence of increasing space velocity is

l. 35 g has no effect on the results obtained, oxidation of methacrolein, except that

Table 4

Example number Composition of the catalyst SV (Hours - ¹ ) Reaction heat - moderation (° C) Metalkrolein conversion (%) Selectivity Methacrylic acid (%) mining (° o) 32nd Mc ^ VιΡι ^^ θ> 2 · ^ ®Ο »2® ^, θ0'2 800 290 94.2 82.2 77.4 33rd Mo _lu \ ₁ P ₁ Cu ₀ , ₂ As ₀ , ₂ Fe ₀ , ₂ 3600 335 93.8 81.7 76.6

comparative example

The pH of the light orange red solution obtained in Example 1 (pH 1.0) was adjusted to 5.3 by addition of 28% aqueous ammonium hydroxide solution. The solution is evaporated to dryness and the residue is ground to a 24-48 mesh grain needle and air-dried at 380 ° C for one hour. A catalyst having the following composition is obtained: (NH ₄ ) ₁ , ₅ Mo ₁₀ V ₁ PJCu ₀ , ₂ As ₀ , ₂ . X-ray diffraction confirmed the formation of the ain55 ammonium salt of the heteropoly acid. The IR spectrum also gives this result. The catalyst is used to produce methacrylic acid in continuous operation. The results are shown in Table 5.

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Table 5

Example number Composition of the catalyst Running Time (Sun) Reakcióhő- moderation (° C) methacrolein conversion (%) Selectivity Methacrylic acid (%) mining (%) First (NH ^ ljjjMojjQVjPjCuQjgASgjg 1 320 90.1 82.1 74.0 15 320 77.8 76.2 59.3

Example 34

Under the conditions set forth in Example 1, the methacrolein was oxidized using the catalyst set forth in Table 6 below, prepared as described in Example 1.

Table 6

Composition of the catalyst Running Time (Sun) Reactions! She'- moderation (° C) Metacrolein Selectivity Methacrylic acid conversion (%) (%) mining (%) MO ₁₀ Y ₂ P ₁ Cu ₀ , ₂ As ₀ , ₂ 1 340 90.1 75.2 67.8 30 340 90.5 75.1 68.0

Patent claims:

Claims (4)

Patent claims: A process for the production of methacrylic acid by oxidation of methacrolein with molecular oxygen or a gas containing molecular oxygen, in a vapor phase, in the presence of a mixed metal catalyst, in a vapor phase, characterized in that Mo _o V ₆ P _c Cu _d As _e X / O _ff Catalysts of Formula H X can represent one or more of tin, lead, cerium, cobalt, iron, zirconium, thorium, tungsten, germanium, nickel, rhenium, bismuth, antimony, chromium, boron, magnesium, silver, aluminum, zinc and titanium, b, c, d, e, f and g represent the atomic ratio of the elements and may have the following meaning: a is 10 b is a number from 0.5 to 2, c is a number from 0.5 to 3, d is a number from 0.05 to 1, e is from 0.05 to 1 is a number 0 or 3 and g is a number defined by the valence and atomic ratio of the other elements. 2. A process as claimed in claim 1 wherein X is one or more of tin, thorium, cerium, tungsten, germanium, rhenium, bismuth, antimony, boron or aluminum. The process according to claims 1 and 2, characterized in that the oxidation is carried out at a temperature of 200-380 ° C. 4. A process according to any one of the preceding claims, wherein the oxidation is carried out in the presence of water vapor.